<template>
  <div>
    <div class="box">
    <p>请选择你要购买的书籍</p>
    <ul>
      <li v-for="(item, index) in arr" :key="index">
        {{ item.name }} <button @click="buy(index)">买它！</button>
      </li>
    </ul>
    <table width="500" cellspacing="0">
      <thead>
        <tr>
          <th>序号</th>
          <th>书名</th>
          <th>单价</th>
          <th>数量</th>
          <th>合计</th>
        </tr>
      </thead>
      <tbody>
        <tr v-for="(item, index) in arr" :key="index">
          <td> {{index+1}} </td>
          <td>{{ item.name }}</td>
          <td>{{ item.price }}</td>
          <td>{{ item.count }} </td>
          <td>{{total(index)}}</td>
        </tr>
      </tbody>
    </table>
    <p>总价格为:{{ allTotal }} </p>
    </div>
  </div>
</template>

<script>
export default {
  data() {
    return {
      arr: [
        {
          name: "水浒传",
          price: 107,
          price: 107,
          count: 0,
        },
        {
          name: "西游记",
          price: 192,
          count: 0,
        },
        {
          name: "三国演义",
          price: 219,
          count: 0,
        },
        {
          name: "红楼梦",
          price: 178,
          count: 0,
        },
      ],
    }
  },
  methods: {
    buy(index){
      this.arr[index].count++
    },
    total(index){
      return this.arr[index].count * this.arr[index].price
    }
  },
  computed:{
     allTotal(){
        let sum = 0
        this.arr.forEach(item=> sum+=item.price*item.count)
        return sum
      }
  }
}
</script>
<style>
table,
table td,
table th {
  border: 1px solid #000;
}
.box {
  width: 600px;
  margin: 0 auto;
}

</style>